Many amputees and partial amputees now wear prosthetic hands incorporating powered and/or non-powered digits. As mobile telephone and device technology has developed in recent years, many of those persons now own a mobile telephone, tablet or other device which has a touchscreen. The touchscreens in the majority of these devices detect a user's input using sensors and circuitry to monitor changes in a particular state of the screen. Many of these devices employ capacitive touchscreens which use a layer of capacitive material to hold an electrical charge, and when the user's finger touches the screen the capacitance at the point of contact changes, thereby indicating at which point the user is touching the screen.
The digits of hand prosthetics are typically formed from stainless steel or a similar metal and are usually covered by some form of protective and/or aesthetic cover formed from an elastomer. The elastomer layer may or may not be covered in certain areas by polyurethane or the like so as to aid donning and removal of the cover. The presence of such covers presents a problem to a prosthetic wearer who wishes to operate the aforementioned touchscreens, as the cover interferes with the ability of the user to change the capacitance when touching the touchscreen. Prosthetic wearers who still have one hand can choose to operate the device with that hand, but this can be inconvenient and is obviously not an option for those who have lost both hands.
It has been established that simply removing the cover from the digit and using the metal digit to touch the screen does not change the capacitance as needed. One solution which has been proposed has been to provide a metal pad or dome at the tip of the digit. However, it has been found that the success of this arrangement is dependent on the specific shape of the contact surface on the digit and also this very often leads to scratching and cracking of the relatively delicate screen after frequent sweeping and tapping motions by the metal pad. Another proposal has been to provide conductive threads in the digit covers, with the threads running along the length of the cover from the tip. However it has been found that repeated folding and extending motions of the digits can cause these threads to wear and break relatively quickly, thereby preventing the required change in capacitance. A further solution has been to connect the digit tip to an external conductive wire. However, running a conductive wire down the entire length of the digit increases the likelihood of the wire fouling upon another component or object or accelerating fatigue in the wire as it is stretched every time the digit is closed, with the result being an increased likelihood of damage to, or failure of, the conductive wire.
It is an aim of the present invention to obviate or mitigate one or more of these disadvantages.